The invention relates to a safety valve device used in a milking installation, in particular for the automatic milking of milk-producing animals, for example cows, sheep, goats etc.
The automatic milking process may be performed by means of so-called milking robots. The safety valve device is provided for protecting and sealing off the lines in which so-called “good milk” (for example, milk intended for sale or feeding to calves) is conducted, and also the “good milk” itself, from undesired media, for example cleaning and flushing media, from lines conducting so-called “bad milk” (for example, adulterated milk), and also for preventing undesired media from being drawn in.
It is necessary to observe and adhere to relevant national regulations and guidelines, for example the American FDA guidelines, which apply to milking installations and milking facilities which come into contact with milk.
Such a safety valve arrangement is also referred to as a “block-bleed-block valve arrangement”. Here, a medium flows through a cavity. The cavity can be closed off at one end by means of a first valve and at another end by means of a second valve. Depending on the flow direction, the valves are referred to as inlet and outlet valves. The cavity itself is provided, for aeration purposes, with a ventilation valve. In a throughflow position, the first and second valves are open so as to permit a flow of the medium through the first and second valves and through the cavity. Here, the ventilation valve is closed. If the first and second valves are closed in order to assume the ventilation position, the ventilation valve must remain closed until the first and second valves are completely closed. Only then can the ventilation valve be opened for the purpose of ventilating the cavity. This also applies in the reverse situation, that is to say when the safety valve device is switched over from the ventilation position into the throughflow position.
WO 2011/028293 A2 describes a safety valve for an automatic milking installation.
Owing to the ever increasing demands in particular for high throughput rates and continuous, low-maintenance operation, or operation with long maintenance intervals, in the case of modern milking installations or milking robots which are complex and expensive, there is a need for improved safety valve devices.